The springs themselves are pretty solid and the top bit gets riveted into the wing which is more than enough to support a plastic bumper Plus just about every car at japfest had them and they look quality haha.
Ive done almost as much as Lew ^^ but PAS is going back in before my car goes on the roads. ABS looks really untidy in Starlets. You can also relocate the washer bottle to the boot and relocate the coolant expansion tank to the back of the bay or whatever.
Not to everyone's taste but, i bought these. http://www.ebay.co.uk/itm/COMPETITION-BONNET-BOOT-BUMPER-SPRING-LATCH-KIT-/390549878653?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item5aee96377d Yet to fit them though.